Line driver for coupling a data transceiver to a line
a data transceiver and line driver technology, applied in the direction of transmission, amplifiers, modulated carrier systems, etc., can solve the problems of inefficiency of the transceiver used in dsl systems, inducing data errors, and reducing the passive impedance in series with the line, so as to maximize the received signal and minimize the dynamic voltage
Inactive Publication Date: 2006-03-30
STMICROELECTRONICS BELGIUM
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Benefits of technology
[0023] This line driver circuit provides an advantage of a synthesized impedance whose accuracy does not decrease as the value of the synthesized impedance increases. It also provides an advantage of maximizing the received signal, while satisfying the constraint of improved, ideally best possible echo cancellation (i.e. no transmit signal on the receive nodes). This second advantage is linked with a minimized dynamic voltage at the output of the amplifier for a given dynamic voltage at the input of the line and this is obtained by connecting the load and the matching impedance between both outputs of the differential amplifier.
Problems solved by technology
If the signal is clipped by the transmitter or receiver, noise is added to the signal which is spread over a wide frequency band and generally has the effect of inducing errors in the data.
Both those requirements make transceivers used in DSL systems quite inefficient.
There are two limitations on reducing the passive impedance in series with the line.
A first limitation is that the degree of reduction is limited by the accuracy of the resistors used for the implementation.
A second limitation is due to the need to couple a receiver to the line.
Nevertheless, this circuit still suffers from the first limitation described above.
Method used
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[0062] The present invention will now be described with reference to certain embodiments and with reference to the above mentioned drawings. Such description is by way of example only and the invention is not limited thereto.
[0063]FIG. 7 shows a line driver circuit 250 which is suitable for use in connecting a transmitter 210 and / or a receiver 220 of a data transceiver, such as a broadband modem, to a transmission line 230 (represented by a load Z), such as a twisted pair line. The modem can operate according to one of the family of Digital Subscriber Line (so-called xDSL) technologies such as Asymmetric Digital Subscriber Line (ADSL). The line driver circuit 250 comprises a differential amplifier which may be formed from two operational amplifiers OA1, OA2, for example. A signal which is to be transmitted +Vi, −Vi is applied to a non-inverting input of each amplifier OA1, OA2.
[0064] There are two sets of feedback paths around the amplifiers OA1, OA2. One set of feedback paths rel...
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A line driver circuit couples a data transceiver to a line. The line driver includes a differential amplifier which receives a signal for transmission on the line. First and second feedback paths connect between outputs of the amplifier and inputs of the amplifier. A bridge couples the differential amplifier to the line. The bridge comprises two matching impedance and two secondary transformer winding. Each matching impedance is connected in series with a secondary transformer winding between the outputs of the amplifiers. Two feedback branches connect between internal nodes of the secondary windings and the inputs of the differential amplifier. The line driver circuit is less sensitive to accuracy of component values while providing an increased dynamic on the line for a given dynamic of the transceiver and a given attenuation of the received signal.
Description
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a line driver for coupling a data transceiver to a line which is particularly useful for, but not limited to, coupling a broadband modem to a transmission line as well as to stationary or portable devices having such a modem, to methods of operating a line driver and producing signals, and methods of offering a communication service over a link having such a modem. [0003] 2. Discussion of the Related Art [0004] Digital Subscriber Line (DSL) transmission systems have become very popular throughout the world for the transmission of data. The high bit rate versus distance characteristic of DSL systems make them convenient systems to provide households and small companies with services such as broadband internet access, video distribution and voice communications. [0005] DSL standards generally use a Discrete MultiTone (DMT) transmission scheme to deliver data over a twisted pair transmission li...
Claims
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Login to View More IPC IPC(8): H04M1/00H04B1/58H04L27/00H04L27/26
CPCH03F3/45475H03F2200/541H04L27/2601H04L27/0002H04B1/581
Inventor LATTE, OLIVIER RENE NICOLAS
Owner STMICROELECTRONICS BELGIUM